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Green-Synthesized ZnO and MgO Nanoparticles Modulate Physiology and Antioxidant Defense in Maize Under Alkaline Stress

MUHAMMAD IFTIKHAR , Anis Shah

Abstract

Alkaline stress severely impairs the growth and yield of Zea mays L. by disrupting physiological and biochemical functions. This study evaluated green-synthesized ZnO and MgO nanoparticles (NPs), prepared using neem and licorice extracts, for mitigating alkaline stress. Nanoparticles were nanosized, crystalline, and functionalized by phytochemicals, confirmed by SEM, FTIR, UV–Vis, and EDX. A pot experiment using NPs (25–200 ppm) under control and alkaline stress assessed morphological, physiological, biochemical, and ionic responses. Alkaline stress reduced root fresh and dry weight to 2.60 and 0.66 g (−59.6%, −31.0%), shoot fresh and dry weight to 2.60 and 0.38 g (−59.6%, −70.0%), chlorophyll a, b, and carotenoids to 1.31, 0.67, and 2.40 mg g⁻¹ (−62.4%, −54.7%, −62.8%), while increasing MDA (244.6%), H₂O₂ (457.7%), and RMP (55.9%). The combined ZnO 50 ppm + MgO 50 ppm treatment improved chlorophyll a, b, and carotenoids to 3.48, 1.48, and 6.45 mg g⁻¹ (165.4%, 120.3%, 168.5%), total soluble protein (392.8%), total protein (301.0%), proline (105.5%), glutathione (35.6%), and ascorbic acid (44.2%). Antioxidant enzymes increased, with SOD at 29.52 U mg⁻¹ (452.8%), POD 24.44 U mg⁻¹ (862%), and APX 51.62 U mg⁻¹ (560%), reducing MDA, H₂O₂, and RMP (−78.1%). High nanoparticle concentrations (200 ppm) were toxic. Moderate ZnO and MgO NP doses enhanced resilience, yield stability, and sustainable agriculture.

FP25200  Accepted 04 September 2025

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